21st.dev UI Skill

21st.dev is a marketplace of 10,000+ production-ready React/Tailwind (shadcn-compatible) components, plus AI UI generation. This skill drives the 21st MCP server.

When to reach for it

• The user asks to add/build a UI element: "add a pricing section", "I need a nice navbar", "make a testimonials block".
• The user wants options or inspiration before committing to a design.
• The user needs a company logo in JSX/TSX (search_logo).
• The user wants brand-new UI generated from a description (generate).

Workflow: install an existing component (default path)

Prefer real catalog components over writing UI from scratch — they ship with dependencies, demos, and responsive/dark-mode support.

1. search with a short natural query (e.g. "pricing table", "animated hero"). Results include names, descriptions, previews, and install ids.
2. Pick the best match for the user's stack and style; show the user 1–3 top candidates if the choice isn't obvious.
3. get_component to fetch the full code and metadata for the chosen item.
4. Install into the project the way the result instructs (shadcn-style registry add or by writing the returned files), then wire it into the page and adapt tokens/props to the project's design system.

Notes:

• Free tier allows catalog search and 2 component installs per day; paid components return code only after unlock.
• Match the project's existing conventions (Tailwind config, cn helper, component folder layout) when integrating.

Workflow: generate new UI

When nothing in the catalog fits or the user explicitly wants custom UI:

1. Check get_usage.aiGenerationEnabled and the current tools/list. Paid component access alone does not enable hosted AI. Missing or unknown status is not permission to generate.
2. With AI off, use search and get_component, then implement or adapt the UI with your own coding agent. Do not call generation tools, legacy builder/refiner aliases, or the CLI as a workaround.
3. When AI is enabled and generate is listed, call it with the purpose, layout, content, style, and stack constraints. It consumes AI credits and returns a preview URL; open that URL to view the generation.
4. For existing sketch drafts, use get_generation and get_take to read their code. These reads remain available with AI off.

If a cached call returns ai_subscription_required, stop generation attempts. After enabling AI, refresh the tool list or reconnect before trying again. The entitlement flag does not report the remaining credit balance.

Logos

search_logo returns brand logos as ready-to-paste JSX/TSX — one brand per call.

Setup and auth

The server is HTTP MCP at https://21st.dev/api/mcp, authenticated with the x-api-key header. Keys are free and instant at https://21st.dev/mcp. If a call fails with an auth error, tell the user to grab a key there and set it in the plugin configuration (variable API_KEY_21ST).

Legacy Magic tool names (21st_magic_component_builder, logo_search, ...) are still accepted server-side, but prefer the current names: search, get_component, generate, get_inspiration, search_logo.